Examples: Vulkan: Viewport: Tweak to improve framerate on multiple-viewport situations, tho it is still halving the unthrottled framerate on nvidia for some reason.. Followup to 4dea032 (#1542)

examples/imgui_impl_vulkan.cpp

@@ -1113,14 +1113,16 @@ static void ImGui_ImplVulkan_CreateWindow(ImGuiViewport* viewport)
         exit(-1);
     }
 
-    // Get Surface Format
+    // Select Surface Format
     const VkFormat requestSurfaceImageFormat[] = { VK_FORMAT_B8G8R8A8_UNORM, VK_FORMAT_R8G8B8A8_UNORM, VK_FORMAT_B8G8R8_UNORM, VK_FORMAT_R8G8B8_UNORM };
     const VkColorSpaceKHR requestSurfaceColorSpace = VK_COLORSPACE_SRGB_NONLINEAR_KHR;
     wd->SurfaceFormat = ImGui_ImplVulkanH_SelectSurfaceFormat(g_PhysicalDevice, wd->Surface, requestSurfaceImageFormat, (size_t)IM_ARRAYSIZE(requestSurfaceImageFormat), requestSurfaceColorSpace);
 
-    // Get Present Mode
-    VkPresentModeKHR present_mode = VK_PRESENT_MODE_IMMEDIATE_KHR;
-    wd->PresentMode = ImGui_ImplVulkanH_SelectPresentMode(g_PhysicalDevice, wd->Surface, &present_mode, 1);
+    // Select Present Mode
+    // FIXME-VULKAN: Even thought mailbox seems to get us maximum framerate with a single window, it halves framerate with a second window etc. (w/ Nvidia and SDK 1.82.1)
+    VkPresentModeKHR present_modes[] = { VK_PRESENT_MODE_MAILBOX_KHR, VK_PRESENT_MODE_IMMEDIATE_KHR, VK_PRESENT_MODE_FIFO_KHR };
+    wd->PresentMode = ImGui_ImplVulkanH_SelectPresentMode(g_PhysicalDevice, wd->Surface, &present_modes[0], IM_ARRAYSIZE(present_modes));
+    //printf("[vulkan] Secondary window selected PresentMode = %d\n", wd->PresentMode);
 
     // Create SwapChain, RenderPass, Framebuffer, etc.
     wd->ClearEnable = (viewport->Flags & ImGuiViewportFlags_NoRendererClear) ? false : true;